1. Field of the Invention
The present invention relates to a composition for metallizing the surface of ceramics, such as nitride, oxide and the like.
2. Description of the Related Art
As a prior art for metallizing the surface of ceramics, there is known only a "Mo-Mn method" which utilizes "20% by weight of Mn and the balance of Mo" as a metallizing composition when the ceramics to be metallized is an alumina ceramics including more than several % by weight of a glass phase. In this case, if the ceramics to be metallized contains only a slight amount of the glass phase, a certain % by weight of SiO.sub.2, talc or other oxide is added to the above composition as a metallizing composition.
To metallize the surface of ceramics, the metal powder of the metallizing composition, Mo and Mn, is suspended and mixed in a paste forming solution with nitrocellulose and other organic solvents. The mixed paste is coated on the surface of ceramics and then sintered in a wet hydrogen atmosphere having a dew-point in the range of -5.degree. C. to 20.degree. C. at a temperature of from 1300.degree. to 1500.degree. C. In this case, the forming of the metallized layer occurs because, when the metallizing composition and the alumina ceramic substrate containing the glass phase are sintered, a low melting glass is formed by MnO produced through oxidation and Al.sub.2 O.sub.3 in the alumina ceramics, which penetrates into voids in the Mo layer and then is bonded to the surface of the ceramics by cooling.
This prior art, however, can not be applied to ceramics sintered bodies of newly developed sintered nitride and oxide ceramics which have an excellent strength, such as Si.sub.3 N.sub.4, AlN, SIALON, partially stabilized Zirconia, and the like, high purity sintered alumina ceramics having a purity of 99.0% or more, and ceramics containing substantially no glass phase. Therefore, the prior art is not satisfactory as a preliminary treatment when brazing the ceramics to the metal through a brazing alloy.